Osama bin Laden lies at the bottom of the Arabian Sea. Anwar al-Awlaki was taken out by a Hellfire missile in Yemen. And now al-Qaeda’s second-in-command, Abu Yahya al-Libi, has been confirmed killed in Pakistan.

Since last year, U.S. counterterrorism operations have systematically stripped al-Qaeda of its leaders. Except for Ayman Al-Zawahiri, who has been reduced to the role of video propagandist, little remains of al-Qaeda’s central core.

Al-Libi was the target of a U.S. missile strike near the Afghanistan border in Pakistan’s North Waziristan region on Monday. His death is al-Qaeda’s most significant loss since U.S. Navy SEALs killed bin Laden.

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“Al-Libi’s death is a major blow to core al-Qaeda, removing the number two leader for the second time in less than a year, and further degrading the group’s morale and cohesion, and bringing it closer to its ultimate demise than ever before,” White House spokesman Jay Carney told reporters Tuesday.

‘The radicalization phenomenon is now almost enshrined in some of our vulnerable communities’

But terrorism expert Bruce Hoffman, director of security studies at Georgetown University, said while al-Libi’s death was a step forward, “I don’t think the core is finished — weakened, but still able to replenish their ranks.”

And while the terrorists behind the 9/11 attacks are rapidly realizing their martyrdom dreams, the violent intolerance they promoted still lingers within regional al-Qaeda affiliates in places like Yemen as well as in Western countries.

Although al-Libi’s death has further diminished al-Qaeda’s ability to plan and organize attacks, the threat had already been shifting away from bin Laden’s organization to the increasingly scattered followers of his bigoted ideology.

Widely considered the most dangerous of those is Al Qaeda in the Arabian Peninsula, which has tried several attacks in the West, notably the underwear bomber’s attempt to bring down a flight bound for Detroit.

The Somali group Al-Shabab, which has declared itself part of al-Qaeda, is also a top concern among Western security officials. The group has called for Canada to be targeted, and last week two men trained by Al-Shabab were arrested in Denmark for allegedly planning attacks.

The shifting threat has posed new challenges for Canadian security officials, who have found themselves preoccupied with young, Canadian extremists who either want to travel abroad to join terror groups or, like the Toronto 18, want to attack Canada itself.

“The radicalization phenomenon is now almost enshrined in some of our vulnerable communities. We are seeing more and more individuals travelling abroad,” the RCMP’s top national security officer, Assistant Commissioner Gilles Michaud, told the Special Senate Committee on Anti-Terrorism in April.

“The other piece around the evolution of the threat is that we have had significant changes since a year and a half ago. We have to think about AQ core, how AQ core has been affected and the impact it has had where some of its affiliates have taken a more significant role. It is a bit more of a complex environment around being able to track who is doing what and who is where.”

Seth Jones, an analyst at Rand Corp., said al-Libi had been the “gatekeeper” between the al-Qaeda leadership and affiliates in Yemen, Somalia, Iraq and North Africa. “His death does make it more difficult for the Pakistan leadership to communicate with the field,” he told the BBC.

But al-Qaeda’s affiliates are not dependent on the central core of al-Qaeda. Indeed, documents recovered from bin Laden’s compound in Pakistan show he was frustrated by their actions and lamented that they were damaging the al-Qaeda brand by killing so many Muslims.

A 49-year-old Libyan, al-Libi was captured in 2002 and held at the Bagram air base in Afghanistan but escaped in 2005. A cleric as well as a terrorist, he had appeared in videos urging followers to attack the West.

“Al-Libi is a key motivator in the global jihadi movement and his messages convey a clear threat to U.S. persons or property worldwide,” reads the Rewards for Justice website, which had offered $1-million for information leading to his capture.